A number of types of polymeric materials are known to be useful in contact lens manufacture. In general contact lens materials can be thought to fall into one of the following classifications: soft hydrophilic, soft, non-hydrophilic, and a more recent development, hard gas permeable. Gas permeable materials typically comprise polymeric materials formed by copolymerizing polyorganosiloxane monomers with various other monomers. These polymeric materials possess high oxygen permeabilities which make them particularly attractive as contact lens materials. In general, they are not as hydrophilic as the soft hydrophilic materials, and thus they are not as easily "wetted". These soft, non-hydrogels are illustrated by the following patents:
U.S. Pat. No. 4,153,641 discloses acrylate functional endcapped polyorganosiloxanes which can be polymerized to form high oxygen permeable polymeric networks, or which can be copolymerized with other monomers to form high oxygen permeable copolymers. Specific comonomers disclosed include low esters of acrylic acid, a methacrylic acid, styryls and N-vinyl pyrrolidinone.
U.S. Pat. No. 4,208,506 discloses soft contact lenses made from polymers and copolymers comprising polyparaffinsiloxane polymers and copolymers formed by polymerizing a polyparaffinsiloxane monomer alpha, omega terminally bonded through divalent hydrocarbon groups to polymerized, free radical polymerizably activated, unsaturated groups forming a polymer in a crosslinked network. Additionally, specific comonomers are disclosed which include lower esters of acrylic and methacrylic acid, styryls and N-vinyl pyrrolidinone which may be copolymerized with the above-described polyparaffinsiloxane monomer to form a copolymer.
U.S. Pat. No. 4,303,772 discloses polysiloxanyl alkyl esters of acrylic and methacrylic acids and its copolymerization with alkyl esters of acrylic, methacrylic acids and/or itaconate esters to produce highly permeable contact lens material. The copolymer preferably includes a crosslinking agent and hydrophilic monomer. Contact lenses manufactured from the material are easily machined and polished into hard or semi-hard contact lenses having excellent dimensional stability.
U.S. patent No. 4,330,383 discloses improved contact lens materials are obtained from copolymers containing a siloxanyl alkyl ester vinyl monomer by exposing the materials to high energy radiation thereby reducing the amount of unreacted monomer and residual contaminants.
U.S. Pat. No. 4,327,203 discloses articles for biomedical applications made from a polymer formed by polymerizing (a) one or more polysiloxane monomers alpha, omega terminally bonded through divalent hydrocarbon groups to an activated, unsaturated group with (b) a cycloalkyl modulus modifier, e.g. tertiary butyl cyclohexyl methacrylate, menthyl acrylate or methylisopentyl cyclooctyl acrylate, and (c) a tear film stabilizer. The products are useful as hard contact lenses. U.S. Pat. No. 4,341,889 discloses the modulus modifier above can be tertiary butyl styrene. U.S. Pat. No. 4,355,147 discloses the modulus modifier above can be polycyclic acrylate or methacrylate such as isobornyl methacrylate, adamantyl acrylate or isopinocamphyl methacrylate.
U.S. Pat. No. 4,652,622 discloses polymeric materials comprised of monomeric polysiloxanes end capped with activated unsaturated groups, a modulus modifier and small amount of an internal wetting agent such as N-alkenoyltrialkylsilyl aminate.